Vibration damping apparatus for reciprocating drive and cutting head

ABSTRACT

A vibration damping device is described that dampens vibration produced during the conversion of rotational motion into reciprocal motion. The damping is performed using a simple structure wherein first and second conversion mechanisms are symmetrically arranged with respect to a plane of symmetry, first and second rotating shafts rotate opposite to each other at a constant speed, and the rotational motion is converted into reciprocal motion. The total of mass acting on gravity centers of a first balancer and a second balancer is approximately equal to the total of mass reciprocally driven by a first driving shaft and a second driving shaft. Both gravity centers are positioned 180 degrees to the first driving shaft and second driving shaft across the axes of the first rotating shaft and second rotating shaft. As a consequence, the forces in the direction of an axis can be balanced suppressing vibration.

TECHNICAL FIELD

The present invention relates to a vibration damping apparatus forreciprocating drive for damping vibration occurring upon conversion ofrotary motion into fast reciprocal motion in order to reciprocally drivea cutting blade of a cutter or so, and cutting head.

BACKGROUND ART

Conventionally, conversion mechanisms such as crank mechanisms arebroadly used for conversion between rotary motion and linear reciprocalmotion. Even though reciprocal motion can be directly caused, driving inone direction and then driving in the reverse direction requires astoppage in the course thereof, making it difficult to increase thespeed. By converting a continuous rotary motion caused by a motor, etc.into a reciprocal motion, it is possible to easily obtain a fastreciprocal motion.

FIG. 11 shows a schematic structure of a cutter 1 requiring a fastreciprocal motion converted from a rotary motion for cutting. In thecutter 1, a cutting blade 6 is reciprocally moved at high speed at thecutting head 5 provided on a guide bridge 4, to clip a cut-part 8 out ofa to-be-cut-sheet 7 on a holding surface 3 above a cutting table 2.Within the cutting head 5, rotary motion is converted into reciprocalmotion. The holding surface 3 in general is rectangular in form. Theguide bridge 4 has a form extending in a direction parallel with theshorter side of the cutting table 2, which is movable in both directionsalong the guides provided on the side edges on the longer sides. Thecutting head 5 is movable in both directions along an extendingdirection of the guide bridge 4. The cutting blade 6 protrudes towardthe holding surface 4 from the cutting head 5. The cutting blade 6 isreciprocally driven in a direction perpendicular to the holding surface3 in a state to pierce through the to-be-cut-sheet 7 held on the holdingsurface 3, thus being allowed to reciprocally move at high speed andangularly displace about an axis parallel with the reciprocal direction.

The holding surface 3 of the cutter 1 is in a state planted withbristles of a material comparatively high in hardness, e.g. syntheticresin. Even in case the cutting blade 6 is inserted piercingly, thebristles deform in a manner avoiding the cutting blade 6 thereby beingprevented from being cut. The guide bridge 4 and cutting head 5 clips acut-part 8 out of the to-be-cut-sheet 7 according to the cutting datainputted to the cutter 1. For such a cutter 1, there is a need toincrease the moving speed of the guide bridge 4 and cutting head 5 andfurther the reciprocation speed of the cutting blade 6 in order toimprove the efficiency of cutting. In order to increase the movingspeed, the cutting head 5 is necessarily reduced in size and weight. Forincreasing the reciprocal speed of the cutting blade 6, there is a needto increase the rotational speed on a drive source of within the cuttinghead 5. However, when converting a rotary motion into a reciprocalmotion within the cutting head 5, vibration readily occurs due to thecomponents, etc. of a motion caused resulting therefrom. Particularly,when reciprocal motion becomes high in speed, vibration increases.

When vibration is encountered in the occurrence of a reciprocal motionin the cutter, there is a fear of increasing the error in a contourcutting a cut-part 8 or causing a fatigue in various regions includingthe cutting blade 6 to be readily broken. In the crank mechanism,because rotary motion is converted into reciprocal motion while couplingthe crank rod at its one end in a position eccentric from the rotaryshaft and regulating the other end of the crank rod in a direction ofreciprocal motion, offset load is applied to the rotary shaft. In caseapplying a load balanced with the load applied to the rotary shaft bythe crank rod to the side opposite to the coupling to the crank rodsandwiching the rotary shaft, the reacting force driving the crank rodcan be canceled to damp vibration (see JP-B-6-53358 and JP-B-7-279, forexample). JP-B-6-53358 discloses a mechanism that a crank rod of a linkmechanism for a counter weight compensating for a load on the crankmechanism is coupled to axial both sides of a crank mechanism forreciprocally moving the cutting blade, to reduce vibration by means of acounter weight provided on the opposite side to the crank mechanism,i.e. opposite by 180 degrees. JP-B-7-279 discloses a mechanism that apair of rotary shafts having balance weights are arranged parallel witha crankshaft of a crank mechanism for reciprocally moving the cuttingblade so that the balance weight is given a weight of a half load, torotate the both balance weights reverse to the crank mechanism therebyreducing vibration.

The mechanism for converting rotary motion into reciprocal motion isused on the sewing machine. As to sewing machines, there are disclosuresof vibration reducing mechanisms (see JP-A-6-154459 and JP-A-7-124361).In JP-A-6-154459, a pair of balancer shafts are arranged above acrankshaft of a needle crank mechanism for reciprocally driving theneedle of a sewing machine, to rotate forward and reverse eccentricbalancers at equal speed and reverse in direction to each other therebyreducing vibration. In JP-A-7-124361, a pair of balancer shafts arearranged on both sides sandwiching a needle crankshaft of a sewingmachine, to provide the needle crank itself with an eccentric center ofgravity to have a balance with a load wherein further the balancershafts in one pair are provided with balancers and rotated reverse tothe needle crankshaft thereby reducing vibration.

In case using a balancer that is a counter weight having a center ofgravity in a position eccentric relative to the rotary shaft,compensation is possible for a static load. However, on the mechanismfor converting rotary motion into reciprocal motion, e.g. a crankmechanism, load varies dynamically even at a constant rotational speed.Accordingly, in case attempted to cancel a load encountered uponconverting rotary motion into reciprocal motion by providing a balanceron the rotary shaft, it cannot be canceled perfectly. In JP-A-6-154459,the needle is moved vertically through one crankshaft. Because avibration damping apparatus mechanism does not operate symmetricallyleft and right about the axis of the needle, balance cannot be obtainedperfectly in the horizontal direction. Even in case the crankshaftbalancer and the rotary shaft balancer are rotated reverse by providingrotary shafts rotating reverse to the crank shaft on both sidessandwiching the crankshaft as in JP-B-7-279 or JP-A-7-124361, thebalancer shafts must be arranged on both sides by being juxtaposed withthe crankshaft. This increases the width of the cutting head, etc. thusmaking size reduction difficult.

In case providing such a link mechanism as to compensate for a loadbased on the crank mechanism on the side opposite, sandwiching thecrankshaft, to the direction that reciprocal motion is caused by thecrank mechanism as in JP-B-6-53358, a cutting head that protrudes acutting blade downward requires a space for a link mechanism in theabove thereof thus resulting in an increased height of the cutting head.Meanwhile, because the cranks are opposed at 180 degrees, in case thelink mechanism is coupled to one lateral direction of a crank axis, acouple of forces occur at axial front and rear of the crank.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide a vibration dampingapparatus for reciprocating drive and cutting head capable of dampingthe vibration resulting from a reciprocal motion by attaining a balanceby means of a simple structure, which can be easily reduced in size.

The invention is a vibration damping apparatus for reciprocating drive,for damping vibration occurring upon conversion of rotary motion intoreciprocal motion, comprising:

a first conversion mechanism for converting a rotary motion of a firstrotary shaft so that a reciprocal motion in a predetermined drivedirection perpendicular to the first rotary shaft is included in a driveposition provided eccentrically from the first rotary shaft;

a second conversion mechanism provided in pair with the first conversionmechanism and arranged symmetric with the first conversion mechanismwith respect to a reference virtual plane parallel with thepredetermined drive direction, for converting a rotary motion of asecondary rotary shaft which rotates at equal speed reverse to and isparallel with the first rotating shaft so that a reciprocal motion inthe drive direction is included in a drive position providedeccentrically from the second rotary shaft, synchronously with areciprocal motion converted by the first conversion mechanism;

a combining mechanism for extracting and combining together reciprocalmotions in the drive direction converted from rotary motions by thefirst conversion mechanism and the second conversion mechanism,respectively;

a first counter weight having a center of gravity in a position on aside symmetric with the drive position with respect to the first rotaryshaft, for taking a balance with an offset load occurring upon motionconversion; and

a second counter weight provided in pair with the first counter weightand having a center of gravity in a position on a side symmetric withthe drive position with respect to the second rotary shaft, for taking abalance with an offset load occurring upon motion conversion.

Furthermore, the invention is characterized by further comprising athird counter weight provided on a third rotary shaft parallel with thefirst rotary shaft and rotating reverse at a rotational speed twice arotational speed of the first rotary shaft, the third counter weightbeing lighter in weight than the first counter weight and eccentric incenter-of-gravity position with respect to the third rotary shaft; and

a fourth counter weight provided in pair with the third counter weightand arranged symmetric with the third counter weight with respect to thereference virtual plane, the fourth counter weight being provided on afourth rotary shaft parallel with the second rotary shaft and rotatingreverse at a rotational speed twice a rotational speed of the secondrotational shaft, the fourth counter weight being lighter in weight thanthe second counter weight and eccentric in center-of-gravity positionwith respect to the fourth rotary shaft.

Furthermore, the invention is characterized in that the combiningmechanism carries out the combining so that the drive direction is onthe reference virtual plane.

Furthermore, the invention is characterized in that the first conversionmechanism and the second conversion mechanism are crank mechanisms eachprovided with a crank rod, respectively, having one end pivotably anddisplaceably coupled to the drive position;

-   -   the combining mechanism including        -   coupling members pivotably and displaceably coupled to other            ends of crank rods of the first conversion mechanism and            second conversion mechanism, respectively, and        -   a guide mechanism for guiding a reciprocal motion combined            by the coupling member, in the drive direction.

Furthermore, the invention is characterized in that center-of-gravitypositions of the first and second counter weights and the drivedirection are on a virtual plane perpendicular to the reference virtualplane.

Furthermore, the invention is characterized by comprising:

a rotation drive source for deriving a rotation output from a drivingpulley;

a first driven pulley provided on the first rotary shaft;

a second driven pulley provided on the second rotary shaft so as to bepaired with the first driven pulley;

an idle pulley provided so as to freely rotate; and

a belt stretched over the driving pulley, the first driven pulley, thesecond driven pulley and the idle pulley, for conveying a rotation driveforce from the driving pulley to the first driven pulley and the seconddriven pulley so that rotational directions of the rotation drive forcebecome different between the first driven pulley and the second drivenpulley.

Furthermore, the invention is a cutting head comprising a vibrationdamping apparatus for reciprocating drive according to any one of theabove ones, the cutting head reciprocally driving a cutting blade on areciprocal motion combined by the combining mechanism.

BRIEF DESCRIPTION OF DRAWINGS

Other and further objects, features, and advantages of the inventionwill be more explicit from the following detailed description taken withreference to the drawings wherein:

FIG. 1 is a schematic front view showing a simplified constitution of avibration damping apparatus for reciprocating drive 9 according to oneembodiment of the invention;

FIG. 2 is a simplified front view showing an operation state of thevibration damping apparatus for reciprocating drive 9 of FIG. 1;

FIG. 3 is a simplified construction of a cutting head 40 incorporatedwith the vibration damping apparatus for reciprocating drive 9 of FIG.1;

FIG. 4 is a simplified front view showing a structure of rotating thevibration damping apparatus for reciprocating drive 9 of FIG. 1;

FIG. 5 is a simplified front view showing a state in which a cuttingblade 46 is connected to the vibration damping apparatus forreciprocating drive in the cutting head 40;

FIG. 6 is a sectional view as viewed at a sectional line VI-VI of FIG.5;

FIG. 7 is a sectional view as viewed at a sectional line VII-VII of FIG.5;

FIG. 8 is a simplified front view showing a schematic structure of avibration damping apparatus for reciprocating drive 60 according toanother embodiment of the invention;

FIG. 9 is a simplified front view showing a structure of rotating thevibration damping apparatus for reciprocating drive 60 of FIG. 8;

FIG. 10 is a simplified front view showing a schematic structure of avibration damping apparatus for reciprocating drive 70 according tofurther another embodiment of the invention; and

FIG. 11 is a perspective view showing a schematic outer structure of aconventional cutter.

BEST MODE FOR CARRYING OUT THE INVENTION

Now referring to the drawings, preferred embodiments of the inventionare described below.

FIG. 1 shows a schematic constitution of a vibration damping apparatusfor reciprocating drive 9 according to one embodiment of the invention.The vibration damping apparatus for reciprocating drive 9 is a dampingapparatus as to the vibration occurring upon conversion of rotary motioninto reciprocal motion in order to reciprocally drive a cutting blade bya cutting head of a cutter, including a first conversion mechanism 10, asecond conversion mechanism 20 and a combining mechanism 30. Thevibration damping apparatus for reciprocating drive 9 in this embodimentis constructed symmetric with respect to a virtual plane 9 a. Namely,the first conversion mechanism 10 and the second conversion mechanism 20are in a mirror relationship with each other with respect to the virtualplane 9 a. The combining mechanism 30 is to extract and combine togetheron-virtual-plane 9 a components out of the components of reciprocalmotion converted from rotary motions by the first conversion mechanism10 and the second conversion mechanism 20, respectively.

The first conversion mechanism 10 delivers a rotary motion of a firstrotary shaft 11 from a first eccentric cam 12 fixed at one end of thefirst rotary shaft 11 to a first crank rod 13, and converts it into areciprocal motion of the first crank rod 13. By coupling the first crankrod 13 to the first rotary shaft 11, an offset load is applied to thefirst rotary shaft 11. The offset load is compensated for by a firstbalancer 14 integrally added as a first counter weight to the firsteccentric cam 12. The first crank rod 13 has, at one end, a drive end 13a pivotably and displaceably coupled to the first eccentric cam 12 bythe first drive shaft 15 provided on the first eccentric cam 12. Thefirst crank rod 13 has, at the other end, a coupling end 13 b pivotablyand displaceably coupled to the first coupling shaft 16.

The second conversion mechanism 20 includes a second rotary shaft 21, asecond eccentric cam 22, a second crank rod 23, a second balancer 24, asecond drive shaft 25 and a second coupling shaft 26, respectively. Thesecond rotary shaft 21, the second eccentric cam 22, the second crankrod 23, the second balancer 24, the second drive shaft 25 and the secondcoupling shaft 26 are equivalent, respectively, to the first rotaryshaft 11, the first eccentric cam 12, the first crank rod 13, the firstbalancer 14, the first drive shaft 15 and the first coupling shaft 16 ofthe first conversion mechanism 10. However, the second rotary shaft 21is to rotate equal in speed but reverse in direction to the first rotaryshaft 11.

The combining mechanism 30 includes a coupling block 31, a knife driveshaft 32, a rotary bearing 33 and a guide mechanism 34. The couplingblock 31 has a first arm 31 a extending toward the first conversionmechanism 10 and coupled to the first coupling shaft 16, a second arm 31b extending toward the second conversion mechanism 20 and coupled to thesecond coupling shaft 26, and a central portion 31 c. The centralportion 31 c holds a rotary bearing 33 for supporting the knife driveshaft 32 in a manner for rotation about an axis 32 a. The axis 32 a ofthe knife drive shaft 32 lies on the virtual plane 9 a. The reciprocalmotions, respectively converted from rotary motions by the firstconversion mechanism 10 and the second conversion mechanism 20, aredelivered to the coupling block 31 through the first crank rod 13 andthe second crank rod 23. Because of the symmetry with respect to thevirtual plane 9 a, the components in the axial direction 32 a only areextracted and combined together. Based on the extracted/combinedcomponents in the direction of axis 32 a, the knife drive shaft 32 isreciprocally driven. A guide mechanism 34 is provided in order to guidethe reciprocal motion of the knife drive shaft 32 in the direction ofaxis 32 a. The guide mechanism 34 allows the knife drive shaft 32 toslidably displace in the direction of axis 32 a and angularly displaceabout the axis 32 a.

However, where the vibration damping apparatus for reciprocating drive 9is not used on a cutting head 5 as shown in FIG. 11 not requiring torotate a cutting blade about an axis or is used on a sewing machine,there is no need to provide a rotary bearing 33. Meanwhile, the guidemechanism 34 satisfactorily allows only for slidable displacement in theaxial direction.

As explained above, the first conversion mechanism 10 is coupled to thefirst crank rod 13 through the first drive shaft 15 in a drive positionprovided eccentric from the first rotary shaft 11, to effect aconversion in a manner including a reciprocal motion in a directionparallel with the axis 32 a as a predetermined drive directionperpendicular to the first rotary shaft 11. The second conversionmechanism 20 is provided in pair with the first conversion mechanism 10and arranged symmetric with the first conversion mechanism 10 withrespect to the reference virtual plane 9 a parallel with the directionof axis 32 a. This converts the rotary motion of the second rotary shaft20, parallel with the first rotary shaft 11 and rotating reverse atequal speed thereto, in a manner including a reciprocal motion in adirection parallel with the axis 32 a synchronously with the reciprocalmotion converted by the first conversion mechanism 10, through thesecond drive shaft 25 in a drive position provided eccentric from thesecond rotary shaft 21. The combining mechanism 30 extracts and combinestogether the reciprocal motions in the direction of axis 32 arespectively converted from rotary motions, by the first conversionmechanism 10 and the second conversion mechanism 20. The firstconversion mechanism 10 and the second conversion mechanism 20 areallowed to take a balance of the force perpendicular to the virtualplane 9 a because of a conversion into reciprocal motions throughrotations mutually symmetric with respect to the virtual plane 9 a.

Incidentally, the first balancer 14 integrally added on the firsteccentric cam 12 has a center of gravity 14 g in a position on a sidesymmetric with respect to the first rotary shaft 11 with a driveposition the drive end 13 a of the first crank rod 13 is to be driven bythe first drive shaft 15 provided on the first eccentric cam 12, thusfunctioning as a first counter weight to take a balance with an offsetload occurring upon conversion of motion. The second balancer 24integrally added to the second eccentric cam 22 is provided in pair withthe first balancer 14, having a center of gravity 24 g positioning on aside symmetric with a drive position where the drive end 23 a of thesecond crank rod 23 is to be driven by the second drive shaft 25provided on the second eccentric cam 22 as to the second rotary shaft21, thus functioning as a second counter weight to take a balance withan offset load occurring upon conversion of motion.

The total mass of the first balancer 14 and second balancer 24 is givennearly equal to the total mass of the members, etc. existing on adelivery path of a drive force for reciprocally driving a subject ofdrive such as a cutting blade through the first eccentric cam 12 andsecond eccentric cam 22, e.g. the first crank rod 13 and second crankrod 23, the first drive shaft 15 and second drive shaft 25, the firstcoupling shaft 16 and second coupling shaft 26, the coupling block 31,the knife drive shaft 32, the rotary bearing 33 and the cutting blade.Because of 180-degree opposite positioning of the center of gravity 14g, 24 g as a center of mass of the first balancer 14 and second balancer24 and the first drive shaft 15 and second drive shaft 25 as a couplingof the first eccentric cam 12 and second eccentric cam 22 to the driveend 13 a, 23 a of the first crank rod 13 and second crank rod 23 bysandwiching the axis of the first rotary shaft 11 and second rotaryshaft 21, force balance can be taken in a drive direction when causing areciprocal motion. This makes it possible to reduce the offset loadoccurring during rotation of the first rotary shaft 11 and second rotaryshaft 21, thus suppressing against the occurrence of vibration.

FIG. 2 shows an operation state of the vibration damping apparatus forreciprocating drive 9 of FIG. 1. (a), (b), (c) and (d) respectively showstates that the first rotary shaft 11 and second rotary shaft 21 changethe angle of rotation at an interval of 90 degrees. Of those, (a) and(c) correspond to the states that the first drive shaft 15 and seconddrive shaft 25 are in positions of bottom and top dead centers,respectively. The first rotary shaft 11 and the second rotary shaft 21has a spacing to be taken narrow in a range that the first eccentric cam12 and the second eccentric cam 22 are not in contact on the side closeto the first balancer 14 and second balancer 24 as shown in (a)-(c) andon the side close to the first drive shaft 15 and second drive shaft 25as shown in (d). The space caused between the first conversion mechanism10 and the second conversion mechanism 20 can be utilized as anaccommodation space for raising the coupling block 31 or the knife driveshaft 32, as shown in (c). Accordingly, with a casing 35 showing onlythe portion supporting the guide mechanism 34 in the figure, the cuttinghead, etc. can be easily reduced in size by reducing the volume toaccommodate the vibration damping apparatus for reciprocating drive 9.

FIG. 3 shows a schematic construction of a cutting head 40 incorporatedwith the vibration damping apparatus for reciprocating drive 9 ofFIG. 1. The cutting head 40, for use on a cutter similar to the cuttinghead 5 shown in FIG. 11, is to convert a rotational drive due to arotation drive section 41 into a reciprocal motion in the axialdirection of a vertical-movement guide shaft 42. The axial direction ofthe vertical-movement guide shaft 42 is parallel with the axis 32 a ofthe knife drive shaft 32. Along a cut-support surface 43 on a cuttingtable of the cutter, a guide bridge 44 moves in X-axis direction as aleft-right direction on the page. The cutting head 40 moves inY-direction perpendicular to the page along the guide bridge 44. Thecutting head 40 is provided with a cut-direction changer 45 capable ofchanging the direction of a cutting edge of a cutting blade 46 about theaxis 32 a. The cut-support surface 43 is nearly horizontal while theaxis 32 a is nearly perpendicular in direction.

The cutting blade 46 is to cut, at its cutting edge 46 a, ato-be-cut-sheet 47 by a reciprocal motion in the direction of axis 32 awhile penetrating through the to-be-cut-sheet 47 supported on thecut-support surface 43. By controlling the movement in X-axis directionby the guide bridge 44, the movement in Y-axis direction by the cuttinghead 40 and direction of the cutting edge 46 a by the cutting-directionchanger 45 according to cut data while reciprocally moving the cuttingblade 46, the to-be-cut-sheet 47 can be cut into a contour formcorresponding to the cutting data. In order to prevent theto-be-cut-sheet 47 from being frictionally raised during ascending ofthe cutting blade 46 in reciprocal motion from the to-be-cut-sheet 47,the to-be-cut-sheet 47 is held down by a presser 48 in the surfacethereof.

The vibration damping apparatus for reciprocating drive 9 is built inthe cutting head 40, as one unit accommodated within the casing 35. Amotor 49, a rotation-drive source, is used as a drive source forreciprocally moving the cutting blade 46. The motor 49 has a rotationoutput shaft attached with a driving pulley 50. A first driven pulley 51and a second driven pulley 52 are respectively attached on the firstshaft 11 and the second shaft 12 of the vibration damping apparatus forreciprocating drive 9. In order to drive the first driven pulley 51 andthe second driven pulley 52 reverse in direction, a rotatable idlepulley 53 is provided. By a timing belt 54, the rotation drive force offrom the driven pulley 50 is conveyed to the first driven pulley 51 andsecond driven pulley 52.

FIG. 4 shows a structure of a rotation drive force transmitter. It isassumed that rotated reverse are the first rotary shaft 11counterclockwise and the second rotary shaft 21 clockwise at equalspeed, similarly to FIGS. 1 and 2. Incidentally, FIG. 4 shows a state asviewed from left in FIG. 3, together with FIGS. 1 and 2. The firstdriven pulley 51 and the second driven pulley 52, attached on the firstrotary shaft 11 and the second rotary shaft 21, require to be drivencounterclockwise and clockwise, respectively. In case the driving pulley50 is clockwise in rotational direction similarly to the second drivenpulley 52, the timing belt 54 basically is stretched over the drivingpulley 50, the second driven pulley 52 and the idle pulley 53. Thetiming belt 54 employs an endless toothed belt having teeth at bothsides of inner and outer peripheries. The first driven pulley 51 isdriven at the outer periphery of the timing belt 54. The idle pulley 53is arranged to increase the length of contact between the first drivenpulley 51 and the outer periphery of the timing belt 54.

The timing belt 54 is provided with teeth at equal pitch in the innerand outer peripheries thereof. The first driven pulley 51 and the seconddriven pulley 52 are provided with teeth in the same number. In case theteeth are provided greater in the number on the driving pulley 50 thanthe teeth of the first driven pulley 51 and second driven pulley 52, therotation speed on the first rotary shaft 11 and second rotary shaft 21can be provided higher than the rotation speed on the motor 49.

FIG. 5 shows a vertical movement structure for cutting in a manner ofpiercing the cutting blade 46 through the to-be-cut-sheet 47 by means ofthe cutting head 40 of FIG. 3. Vertical-movement guide shafts 42 areprovided penetrating through the casing 35 of the vibration dampingapparatus for reciprocating drive 9, serving as guides for verticallydisplacing the cutting blade 46 or the vibration damping apparatus forreciprocating drive 9. The spacing can be narrowed between the firstrotary shaft 11 and the second rotary shaft 21. Meanwhile, because thecoupling block 31 and knife drive shaft 32 are partly accommodatedbetween the first crank rod 13 and the second crank rod 23, the cuttinghead 40 can be reduced in size.

FIG. 6 and FIG. 7 show structures as viewed at sectional lines VI-VI andVII-VII of FIG. 5, respectively. As shown in FIG. 6, the first rotaryshaft 11 and second rotary shaft 21 are arranged, at one end, with afirst eccentric cam 12 and second eccentric cam 22 and, at the otherend, with a first driven pulley 51 and second driven pulley 52. In theintermediate region, rotary bearings 55, 56, 57, 58 are provided toallow smooth rotation. As shown in FIG. 7, there is included an axis 32a of the knife drive shaft 32. Thus, a virtual plane 59 perpendicular tothe virtual plane 9 a as a symmetric plane at the intermediate betweenthe first conversion mechanism 10 and the second conversion mechanism 20passes through the center of gravity 14 g, 24 g of the first balancer 14and second balancer 24, as shown in FIG. 6. Namely, the center ofgravity position 14 g, 24 g of the first balancer 14, as a first counterweight and second balancer 24 as a second counter weight, as well as theaxis 32 a in a drive direction lie on the virtual plane 59 perpendicularto the reference virtual plane 9 a. The virtual plane 59 isperpendicular to the axis of the first rotary shaft 11 and second rotaryshaft 21. Namely, it is possible to align, on the same plane, the loadbased on a reciprocal motion of the knife drive shaft 32 and thecompensation with the counter weight together. Vibrations can beprevented from occurring due to a positional deviation of the same.

FIG. 8 shows a structure of a major part of the vibration dampingapparatus for reciprocating drive 60 as another embodiment of theinvention. In this embodiment, those corresponding to the embodiment inFIG. 1 are attached with like references, to omit duplicatedexplanations. This embodiment includes a third rotary shaft 61, a fourthrotary shaft 62, a third balancer 63 and a fourth balancer 64, which arearranged symmetric with respect to a virtual plane 60 a in the center.The third rotary shaft 61 is to rotate reverse to and at a rotationalspeed twice the first rotation shaft 11. The fourth rotary shaft 62 isto rotate reverse to and at a rotational speed twice the second rotationshaft 21. Because the first rotary shaft 11 and the second rotary shaft21 rotate reverse in direction, the third rotary shaft 61 rotates in thesame direction as the second rotary shaft 21 while the fourth rotaryshaft 62 rotates in the same direction as the second rotary shaft 21.

The third rotary shaft 61 and the fourth rotary shaft 62 arerespectively provided with the third balancer 63 and the fourth balancer64. The third balancer 63 and the fourth balancer 64 are eccentric intheir center-of-gravity positions, to reduce the secondary vibrationhalf in period relative to the period of the basic reciprocal motion.Namely, the third rotary shaft 61 and the fourth rotary shaft 62 arearranged symmetric with respect to the reference virtual plane 60 asimilarly to the symmetric relationship of between the first conversionmechanism 10 and the second conversion mechanism 20, to provide thethird balancer 63 and the fourth balancer 64 that are lighter in weightthan and eccentric in center-of-gravity position relative to the firstbalancer 14 and second balancer 24. Because the third rotary shaft 61and the fourth rotary shaft 62 are rotated at a speed twice the firstrotary shaft 11 and second rotary shaft 21 and reverse to each other,the secondary vibration can be damped that is difficult to damp with thefirst balancer 14 and second balancer 24. The third balancer 14 andfourth balancer 24, because lighter in weight than the first balancer 14and second balancer 24, can be reduced in size. Even in case the thirdrotary shaft 61 and fourth rotary shaft 62 are provided, size increasecan be avoided for the vibration damping apparatus for reciprocatingdrive 60.

FIG. 9 shows a structure for delivering a rotational drive force bymeans of the vibration damping apparatus for reciprocating drive 60. Inthis embodiment, the driving pulley 50 is driven for rotationcounterclockwise. The third rotary shaft 61 and the fourth rotary shaft62 in FIG. 8 are respectively attached with a third driven pulley 66 anda fourth driven pulley 67, thus being allowed for rotation. A timingbelt 65 is provided with teeth at equal pitch in the inner and outerperipheries thereof, similarly to the timing belt 54 shown in FIG. 4. Byplacing the fourth driven pulley 67 on a side close to the second drivenpulley 52, the timing belt 65 is stretched over the driving pulley 50,the first driven pulley 51 and the fourth driven pulley 67. With thefourth driven pulley 67, a path is established to put the outerperiphery of timing belt 65 in mesh with the second driven pulley 52.Namely, the fourth driven pulley 67 has a function corresponding to theidle pulley 53 in FIG. 4. The third driven pulley 66 having the thirdrotary shaft 61 is provided in a position symmetric with the fourthrotary shaft 62 of the fourth driven pulley 67 with respect to thevirtual plane 60 a. A timing belt 67 is stretched between the thirddriven pulley 66 and the second driven pulley 52. In at least the innerperiphery of the timing belt 67, teeth are provided equal in pitch tothe timing belt 65.

The third driven pulley 66 and the fourth driven pulley 67 are providedwith teeth half in the number of the first driven pulley 51 and thesecond driven pulley 52, respectively. When the driving pulley 50rotatively drives the first driven pulley 51 and second driven pulley 52through the timing belt 65, the fourth driven pulley 67 is rotativelydriven in the same direction as and at a twice rotational speed of thefirst driven pulley 51. The second driven pulley 52 is rotatively drivenat an equal speed to and in reverse direction to the first driven pulley51, to drive the third driven pulley 66 in the same direction at twicespeed through the timing belt 67.

FIG. 10 shows a schematic structure of a vibration damping apparatus forreciprocating drive 70 in still another embodiment of the invention. Inthis embodiment, those corresponding to the embodiment in FIG. 1 areattached with like references, to omit duplicated explanations. Thevibration damping apparatus for reciprocating drive 70 in thisembodiment includes a first conversion cam 71 and a second conversioncam 72 that are arranged symmetric with respect to a virtual plane 70 a.The first conversion cam 71 and the second conversion cam 72 arerespectively attached on one ends of the first rotary shaft 11 and thesecond rotary shaft 21. In the first conversion cam 71 and the secondconversion cam 72, a first follower 73 and a second follower 74 arerespectively provided at positions eccentric from the first rotary shaft11 and the second rotary shaft 21, respectively, engaged in a firstgroove cam 76 and a second groove cam 77 of a coupling cam member 75.The coupling cam member 75 is attached with a knife drive shaft 32 atthe center thereof. By a guide mechanism 78, guiding is effected for thereciprocal motion in the direction of axis 32 a.

In also this embodiment, because conversion mechanism of from rotationalmotion into reciprocal motion is effected symmetric with respect to thevirtual plane 70 a by the first conversion cam 71, second conversion cam72 and coupling cam member 75, it is possible to take a force balance ina direction perpendicular to the virtual plane 70 a. Meanwhile, with thefirst conversion cam 71 and second conversion cam 72, a force balancecan be taken in the direction of axis 32 a of reciprocal motion byarranging the center of gravities 14 g, 24 g of the first balancer 14and second balancer 24 in positions 180-degree opposite to the firstfollower 73 and second follower 74 and sandwiching the first rotaryshaft 11 and second rotary shaft 21. Because of the capability to take aforce balance in between the direction of axis 32 a and the directionperpendicular thereto, vibration can be suppressed from occurring.

The vibration damping apparatus for reciprocating drive 60, 70 explainedabove is usable on a cutting head 40 of a cutter shown in FIG. 3,similarly to the vibration damping apparatus for reciprocating drive 9of the FIG. 1 embodiment. Even in case the cutting blade 46 isreciprocated at high speed, e.g. nearly 6000 cycles per minute, thevibration occurred can be damped so that the cutting head 40 can be madecompact. Meanwhile, vibration damping apparatus for reciprocating drive9, 60, 70 is to be used in reciprocally driving a needle of sewingmachine besides on the cutting head 40 of a cutter.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription and all changes which come within the meaning and the rangeof equivalency of the claims are therefore intended to be embracedtherein.

INDUSTRIAL APPLICABILITY

As described above, according to the present invention, a firstconversion mechanism and a second conversion mechanism in a pair arearranged symmetric with respect to a reference virtual plane in order todamp the vibration occurring upon conversion of rotary motion intoreciprocal motion, to rotate a first rotary shaft of the firstconversion mechanism and a second rotary shaft of the second conversionmechanism reverse to each other, thus making it possible to offset anddamp the vibration caused by rotation. Each of the rotary shafts isprovided with a counter weight for converting, at a drive positionprovided eccentric, a rotary motion into a reciprocal motion in a drivedirection parallel with a virtual plane and taking a balance with anoffset load occurring upon converting the motion by having a center ofgravity on a side symmetric with the drive position. The vibrationoccurring upon converting the motion can be reduced and damped by thecounter weight. Because the conversion mechanisms in a pair, at acombining mechanism, extracts and combines together reciprocal motionsin a drive direction respectively converted from rotary motions, it ispossible to cancel and damp the other motion components than those inthe drive direction. Because the conversion mechanisms are providedsymmetric in a manner being in a pair so that the conversion mechanismscan extract and combines together reciprocal motions converted fromrotary motions, the vibration due to reciprocal motion can be dampedwith balancing by a simple structure. Because the rotary shafts aresatisfactorily two, size reduction can be easily done.

Meanwhile, according to the invention, a third rotary shaft and a fourthrotary shaft are arranged symmetric with respect to a reference virtualplane similarly to the symmetric relationship of between the firstconversion mechanism and the second conversion mechanism and providedrespectively with third and fourth counter weights lighter in weightthan the first and second counter weights and eccentric incenter-of-gravity position. Because the third and fourth rotary shaftsare rotated reverse to each other at a speed twice the first and secondrotary shafts, it is possible to damp the secondary vibration thatdamping is difficult by the first and second counter weights. The thirdand fourth counter weights, because lighter in weight than the first andsecond counter weights, can be made smaller in size. Size increase canbe avoided even where third and fourth rotary shafts are provided.

Meanwhile, according to the invention, a reciprocal motion combined bythe combining mechanism is on a symmetric plane concerning the first andsecond conversion mechanisms. Therefore, by utilizing a space causedbetween the first and second conversion mechanisms, a subject ofreciprocal motion can be arranged. Size reduction is possible byreducing the length required in the drive direction.

Meanwhile, according to the invention, the first and second conversionmechanisms arranged symmetric with respect to the reference virtualplane are crank mechanisms having crank rods each having one endpivotably and displaceably coupled to the eccentric drive position.Since the crank rods are to move symmetrically with respect to thereference virtual plane, the motion components different from the drivedirection become in a reverse direction with each other and therebycancel each other. The combining mechanism is pivotably and displaceablycoupled to the other ends of the crank rods of the first and secondconversion mechanisms by means of a coupling member. Because reciprocalmotion is guided into the drive direction by a guide mechanism,reciprocal motions in the drive direction can be easily extracted andcombined together.

Meanwhile, according to the invention, the center-of-gravity position ofthe first and second counter weights and the drive direction are on thesame virtual plane perpendicular to the reference virtual plane. Becausethis virtual plane is perpendicular to the axis of the rotary shaft, theload due to reciprocal motion and the compensation with the counterweight can be aligned to the same position in respect of axiallyfrontward and rearward directions. Vibration is suppressed fromoccurring due to the positional deviation.

Meanwhile, according to the invention, the rotation drive force derivedfrom a rotation drive source to the driving pulley is conveyed to thefirst and second driven pulleys through a belt stretched on first andsecond driven pulleys provided on the first and second rotary shafts andan idle pulley, which makes it possible to rotatively drive the firstand second rotary shafts respectively. Because of using the idle pulley,the belt can be stretched along a path the first driven pulley and thesecond driven pulley are respectively in contact with the both surfacesof the belt, thus making it possible to easily rotate the first drivenpulley and the second driven pulley reverse in direction. The belt, ifusing a toothed timing belt, can be driven at high speed withoutslippage, making it possible to positively rotate the first and secondrotational shafts reverse in direction and damp the vibration.

Furthermore, according to the invention, the cutting blade isreciprocally driven by the provision of a vibration damping apparatusfor reciprocating drive for the cutting head according to any of theabove ones. Accordingly, even when the cutting blade is reciprocallydriven at high speed, vibration is prevented from occurring thus makingit possible to reduce the cutting head size.

1. A vibration damping apparatus for reciprocating drive, for dampingvibration occurring upon conversion of rotary motion, from a rotationoutputting shaft of a rotation drive source, to reciprocal motion in areciprocating drive direction, comprising: a first conversion mechanism,the first conversion mechanism including a first rotary shaft, a firstcounterweight contacting the first rotary shaft, and a first drive shaftcontacting the first counterweight the first drive shaft being connectedto the first counter weight at a first drive position, the first driveposition being eccentric with respect to the first rotary shaft, toconvert a rotary motion of the first rotary shaft to reciprocal motion,via the first drive shaft at the first drive position, in the directionof the reciprocating drive direction, wherein the first counter weighthas a center of gravity in a position on a side symmetric with the firstdrive position with respect to the first rotary shaft, for balancing anoffset load occurring upon motion conversion; a second conversionmechanism, the second conversion mechanism including a second rotaryshaft, a second counterweight contacting to the second rotary shaft, anda second drive shaft contacting the second counterweight, the seconddrive shaft being connected to the second counter weight at a seconddrive position, the second drive position being eccentric with respectto the second rotary shaft, to convert a rotary motion of the secondrotary shaft to reciprocal motion, via the second drive shaft at thesecond drive position, in the direction of the reciprocating drivedirection, the second conversion mechanism being provided in pair withthe first conversion mechanism so as not to be in direct contact withthe first conversion mechanism and arranged symmetric with the firstconversion mechanism with respect to a reference virtual plane parallelwith the reciprocating drive direction and the second rotary shaftrotating at equal speed reverse to and parallel with the first rotaryshaft so that a reciprocal motion in the reciprocating drive directionis included in the second drive position synchronously with a reciprocalmotion converted by the first conversion mechanism, wherein the secondcounter weight provided in pair with the first counter weight has acenter of gravity in a position on a side symmetric with the seconddrive position with respect to the second rotary shaft, for balancing anoffset load occurring upon motion conversion; and a combining mechanismto extract and combine reciprocal motions in the reciprocating drivedirection which is converted from rotary motions by the first conversionmechanism and the second conversion mechanism, respectively, rotarydriving force from the rotation drive source being transmitted via abelt to the first conversion mechanism and the second conversionmechanism.
 2. The vibration damping apparatus for reciprocating drive ofclaim 1, further comprising: a third counter weight provided on a thirdrotary shaft parallel with the first rotary shaft and rotating reverseat a rotational speed twice a rotational speed of the first rotaryshaft, the third counter weight being lighter in weight than the firstcounter weight and eccentric in center-of-gravity position with respectto the third rotary shaft; and a fourth counter weight provided in pairwith the third counter weight and arranged symmetric with the thirdcounter weight with respect to the reference virtual plane, the fourthcounter weight being provided on a fourth rotary shaft parallel with thesecond rotary shaft and rotating reverse at a rotational speed twice arotational speed of the second rotational shaft, the fourth counterweight being lighter in weight than the second counter weight andeccentric in center-of-gravity position with respect to the fourthrotary shaft.
 3. The vibration damping apparatus for reciprocating driveof claim 1, wherein the combining mechanism carries out the combining sothat the drive direction is on the reference virtual plane.
 4. Thevibration damping apparatus for reciprocating drive of claim 1, whereinthe first conversion mechanism and the second conversion mechanism arecrank mechanisms each provided with a crank rod, respectively, the crankrod for the first conversion mechanism having one end pivotably anddisplaceably coupled to the first drive position via the first driveshaft and the crank rod for the second conversion mechanism having oneend pivotably and displaceably coupled to the second drive position viathe second drive shaft; the combining mechanism including couplingmembers pivotably and displaceably coupled to other ends of crank rodsof the first conversion mechanism and second conversion mechanism,respectively, and a guide mechanism for guiding a reciprocal motioncombined by the coupling member, in the drive direction.
 5. Thevibration damping apparatus for reciprocating drive of claim 4, whereincenter-of-gravity positions of the first and second counter weights andthe drive direction are one a virtual place perpendicular to thereference virtual plane.
 6. A cutting head comprising: the vibrationdamping apparatus for reciprocating drive according to claim 1, thecutting head reciprocally driving a cutting blade on a reciprocal motioncombined by the combining mechanism.
 7. The vibration damping apparatusfor reciprocating drive of claim 2, wherein the combining mechanismcarries out the combining so that the drive direction is on thereference virtual plane.
 8. The vibration damping apparatus forreciprocating drive of claim 2, wherein the first conversion mechanismand the second conversion mechanism are crank mechanisms each providedwith a crank rod, respectively, the crank rod for the first conversionmechanism having one end pivotably and displaceably coupled to the firstdrive position via the first drive shaft and the crank rod for thesecond conversion mechanism having one end pivotably and displaceablycoupled to the second drive position via the second drive shaft; thecombining mechanism including coupling members pivotably anddisplaceably coupled to other ends of crank rods of the first conversionmechanism and second conversion mechanism, respectively, and a guidemechanism for guiding a reciprocal motion combined by the couplingmember, in the drive direction.
 9. The vibration damping apparatus forreciprocating drive of claim 3, wherein the first conversion mechanismand the second conversion mechanism are crank mechanisms each providedwith a crank rod, respectively, the crank rod for the first conversionmechanism having one end pivotably and displaceably coupled to the firstdrive position via the first drive shaft and the crank rod for thesecond conversion mechanism having one end pivotably and displaceablycoupled to the second drive position via the second drive shaft; thecombining mechanism including coupling members pivotably anddisplaceably coupled to other ends of crank roads of the firstconversion mechanism and second conversion mechanism, respectively, anda guide mechanism for guiding a reciprocal motion combined by thecoupling member, in the drive direction.
 10. A cutting head comprising:the vibration damping apparatus for reciprocating drive according toclaim 2, the cutting head reciprocally driving a cutting blade on areciprocal motion combined by the combining mechanism.
 11. A cuttinghead comprising: the vibration damping apparatus for reciprocating driveaccording to claim 3, the cutting head reciprocally driving a cuttingblade on a reciprocal motion combined by the combining mechanism.
 12. Acutting head comprising: the vibration damping apparatus forreciprocating drive according to claim 4, the cutting head reciprocallydriving a cutting blade on a reciprocal motion combined by the combiningmechanism.
 13. A cutting head comprising: the vibration dampingapparatus for reciprocating drive according to claim 5, the cutting headreciprocally driving a cutting blade on a reciprocal motion combined bythe combining mechanism.
 14. A vibration damping apparatus forreciprocating drive, for damping vibration occurring upon conversion ofrotary motion into reciprocal motion, comprising: a first conversionmechanism to convert a rotary motion of a first rotary shaft so that areciprocal motion in a drive direction perpendicular to the first rotaryshaft is included in a drive position provided eccentrically from thefirst rotary shaft, the first conversion mechanism including a firstcounter weight having a center of gravity in a position on a sidesymmetric with the drive position with respect to the first rotaryshaft, for balancing an offset load occurring upon motion conversion; asecond conversion mechanism, provided in pair with the first conversionmechanism and arranged symmetric with the first conversion mechanismwith respect to a reference virtual plane parallel with the drivedirection, to convert a rotary motion of a secondary rotary shaft whichrotates at equal speed reverse to and is parallel with the firstrotating shaft so that a reciprocal motion in the drive direction isincluded in a drive position provided eccentrically from the secondrotary shaft, synchronously with a reciprocal motion converted by thefirst conversion mechanism, the second conversion mechanism including asecond counter weight provided in pair with the first counter weight andhaving a center of gravity in a position on a side symmetric with thedrive position with respect to the second rotary shaft for balancing anoffset load occurring upon motion conversion; a combining mechanism toextract and combine together reciprocal motions in the drive directionconverted from rotary motions by the first conversion mechanism and thesecond conversion mechanism, respectively; a rotation drive source todrive a rotation output from a driving pulley; a first driven pulleyprovided on the first rotary shaft; a second driven pulley provided onthe second rotary shaft so as to be paired with the first driven pulley;an idle pulley provided so as to freely rotate; and a single looped beltstretched over the driving pulley the first driven pulley, the seconddriven pulley and the idle pulley, to convey a rotation drive force fromthe driving pulley to the first driven pulley and the second drivepulley, so that rotational directions of the rotation drive force becomedifferent between the first driven pulley and the second driven pulley.15. A cutting head comprising: the vibration damping apparatus forreciprocating drive according to claim 14, the cutting head reciprocallydriving a cutting blade on a reciprocal motion combined by the combiningmechanism.